In the OLED display device, current for driving the light emitting device to emit light is affected by drift of the threshold voltage of the driving transistor, thereby the brightness during display will change and the display effect is affected.
In existing solutions, typically a compensation module for compensating the threshold voltage of the driving transistor is incorporated in the gate driving circuit of an OLED display device, so as to improve brightness uniformity of the display device during display. In these solutions, generally a plurality of thin film transistors and/or capacitors is included in the compensation module, which reduces the aperture ratio of the display device.
Besides above manner, a so-called Scan Power, in which AC signal is used as power signal (VDD) for the gate driving circuit, can be adopted. In this manner, the number of thin film transistors and/or capacitors is not increased, thereby the aperture ratio of the display device can be improved compared to above manner.
However, in a gate driving circuit formed by N-type thin film transistor, due to limitation of characteristics of the N-type thin film transistor, it is difficult to provide direct output of AC signal VDD, therefore it is difficult to adopt the above-described Scan Power technology to compensate threshold voltage of the driving transistors.